Spacecraft such as communications satellites may be subjected to several discrete shock events during launch into orbit. For example, a spacecraft carried by a launch vehicle may be subjected to shock during separation of the boosters from the launch vehicle and during staging of the launch vehicle. The spacecraft may also be subjected to shock during separation of the spacecraft from the launch vehicle and during deployment of subsystems such as solar panels once the spacecraft is inserted into orbit.
Pyrotechnic or explosive materials are used extensively in space launches to facilitate the above-mentioned separation and deployment events. The release of explosive energy during a separation or deployment event may result in the generation of a shock pulse of relatively short duration and high magnitude. For example, the shock pulse may have a duration of from 50 microseconds to no more than 20 milliseconds. In addition, the shock pulse may have a frequency range of up to 1,000,000 Hz and a peak amplitude (e.g., acceleration) of up to 300,000 g's. Such relatively high intensity shock pulses may be transmitted to sensitive components and instrumentation that may be mounted to the spacecraft and the launch vehicle.
In order to ensure that such components are capable of withstanding high-intensity shock pulses during a launch, individual components are typically subjected to qualification testing in a laboratory environment or other controlled environment. During qualification testing, a component may be subjected to a shock pulse simulating the pyrotechnic shock expected to occur in the service environment (e.g., on the launch vehicle). The pyrotechnic shock to be simulated is typically characterized using a specified or desired shock response spectrum (SRS). The desired SRS may be developed by measuring the response (e.g., the accelerations) of simulated or actual system structure to pyrotechnic shock using live ordnance. For example, a desired SRS may be developed representing the pyrotechnic shock transmitted to a communications satellite mounted on a payload attach fitting of a launch vehicle. The desired SRS may envelope the composite of all the pyrotechnic shock(s) that occur during a flight sequence. For example, the desired SRS may include the shock that occurs during separation of the rocket motors from the launch vehicle, the shock during separation of the fairing from the launch vehicle, the shock during detonation of a pyrotechnic bolt cutter to release a clamp band securing the satellite to the payload attach fitting to allow the satellite to separate from the launch vehicle, and other shock events.
Existing systems and methods for simulating pyrotechnic shock during qualification testing of a component include the use of measured quantities of ordnance in a laboratory environment. The ordnance may be attached to a structure upon which the component or a mass model of the component may be mounted. The ordnance may be detonated in an attempt to generate a shock pulse that results in an acceleration response in the structure that duplicates the desired SRS. Unfortunately, shock pulses generated using such method may be imprecise due to difficulty in quantifying the potential energy contained in a measured quantity of ordnance (i.e., explosive) charge. In addition, shock pulses generated from live ordnance may be difficult to control resulting in time-consuming repeat testing using different quantities of live ordnance on a trial-and-error basis until achieving an acceleration response that is within acceptable limits of the desired SRS.
Furthermore, because the desired SRS may envelope several different shock events with varying frequency content, testing using live ordnance may result in over-testing of a test article which may result in damage to expensive test hardware and requiring failure analysis, and repair, rework, or redesign of the hardware followed by re-testing. Reducing the quantity of ordnance to avoid over-testing may result in under-testing of the test article wherein the shock magnitudes are less than the levels specified for the qualification test. A further drawback associated with the use of explosive materials for qualification testing is that elaborate measures may be required for safe handling and storage of the materials.
Existing systems for simulating pyrotechnic shock may also include the use of mechanical impact to generate a shock pulse in a structure to which a component under test may be mounted. Unfortunately, the mechanical impact method presents challenges in accurately reproducing a desired acceleration in the structure from one mechanical impact to another. In addition, the mechanical impact method may result in mechanical ringing or residual shock response in the structure at the termination of the primary shock pulse. Such mechanical ringing may not otherwise occur in the actual flight structure due to absorption, dampening, attenuation, or distribution of shock that may be available in the actual flight structure. In this regard, such mechanical ringing that may occur in the impact method may result in inaccurate simulation of the pyrotechnic shock.
As can be seen, there exists a need in the art for a system and method for accurately simulating high-intensity pyrotechnic shock with a desired SRS that envelopes several different shock events with varying frequency content. Furthermore, there exists a need in the art for a system and method for simulating high-intensity pyrotechnic shock which can be precisely controlled with excellent repeatability and which is low in cost.